The purpose of this Phase 1/2 study is to find the safest highest dose of SL-401 that can be given to subjects with myeloproliferative neoplasms. This study will also look at how SL-401 stops or slows cancer cell growth and how SL-401 enters and leaves your body. This study will also look at certain proteins in your blood and bone marrow (the soft, sponge-like tissue in the center of most bones) and how the amounts of them might change after receiving SL-401, or might be related to how well SL-401 does or does not function against the cancer. 

There are 2 stages involved with this research study. Nine subjects received SL-401 during stage 1 of the study before the second portion of the study (stage 2) began; a larger number (approximately 36) of the subjects will receive investigational SL-401 during stage 2 of the study. 

Stage 1 of the study is the dose escalation portion to understand the highest dose of SL-401 that may be given safely. The stage 1 portion is now closed to enrollment. Stage 2 of the study will test the highest dose of SL-401 that can be administered safely, as determined during stage 1 of the study, or a lower dose if it can be determined that such a dose has a higher chance of controlling the cancer without causing side effects.

SL-401 will be given by means of an injection through a vein (intravenous injection). Each subject’s dose is calculated based on body weight.

If you are eligible for the study you may receive up to 7 cycles of SL-401 at the research clinic/hospital: cycles 1-4 will last for 21 days; cycles 5-7 will last for 28 days; and any subsequent cycles will last for 42 days.